This is part of a seriesexamining health repercussions for Canadians due to a changing climate.

Today's topic: Air quality. The latest report from the Intergovernmental Panel on Climate Change notes that pollen seasons are changing and in some places are beginning earlier.

Asthma and allergy rates are on the rise across Canada, according to a chorus of environmental experts and advocacy groups. Mounting evidence shows that the hay-fever season now lasts up to a month longer than in the past, and parts of Canada that were once too cold for ragweed and other allergy-inducing plants are now seeing activity for the first time.

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Although the research linking climate change to respiratory health risks is still a relatively new area of study compared with the damage air pollution causes to the heart, the available evidence has many concerned enough to act: This week, the Asthma Society of Canada will host its first national summit focusing on the environment, asthma and allergies, featuring Environment Minister Leona Aglukkaq as keynote speaker. (Ms. Aglukkaq declined a request for an interview.)

The conference comes as the Asthma Society of Canada is reinventing itself as an organization dually focused on the environment and health.

"[Asthma] is an environmentally related disease," said Robert Oliphant, president and CEO of the asthma society. "Our mandate is changing."

Already, Dr. Oliphant said, the rates of people with severe forms of asthma are climbing, and climate change will exacerbate symptoms in many, placing an added burden on the already stretched health-care system.

Dr. Oliphant noted that the most vulnerable Canadians, including families on low incomes and many aboriginal people (those who are more likely to live closer to industrial areas, highways or forests that could be swept by wildfire) are currently feeling the effects the most.

Canada's leading expert on the impacts of climate change on respiratory health, Michael Brauer, said increased pollen production and a longer hay-fever season will cause more allergy symptoms, leading to lost productivity and poor sleep in many individuals. While allergies might seem like a minor inconvenience, he said that hay fever can be "devastating" to those experiencing it. And as more people develop asthma and other respiratory problems because of climate change, the more the health-care system will feel the strain.

"This isn't trivial," said Dr. Brauer, a professor in the school of population and public health at the University of British Columbia. Part of the challenge, he said, is making people understand that regardless of where they live, they will feel the effects of climate change on respiratory health.

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And the case for taking action to stop or reverse these trends may be a hard sell, considering that it will likely take decades of work on issues such as reducing greenhouse-gas emissions and developing plans to reduce traffic congestion before real improvements in air quality are seen, Dr. Brauer said.

A paper published last year in the journal Chest declared that climate change "is a health threat no less consequential than cigarette smoking." Patients with asthma, chronic obstructive pulmonary disease and other lung problems will die earlier and be in worse health because of pollution, forest fires, pollen and floods, the authors say.

The risks are no longer theoretical, said Christopher Carlsten, associate professor and chair in occupational and environmental lung disease at the University of British Columbia. The challenge now, he said, is communicating these risks to the public.

Erika Ladouceur, 25, understands all too well.

She has asthma, is allergic to dust and mould, and feels the effects of changes in humidity, smog and pollen. It affects her daily life and she fears it will only get worse as the climate continues to change.

When Ms. Ladouceur lived in Montreal, she couldn't leave the house on days when it was smoggy. Now she lives in Victoria, where rain, mould and humidity cause her asthma to flare up. She must take asthma medication at least twice a day to control her symptoms and when it's humid, she often must take a steroidal drug.

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"With more things happening and things changing, it means that people like me who are already sensitive are going to be affected even more," she said. "People need to realize that it is happening."

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